Royal Icing On Cookies

How can I tell if I'm putting my RI on too thick or too thin on my cookies?? I border and then flood, but think I am using too much frosting. Any expert advise is appreciated. I do cakes and fairly new to cookies but love doing them. Thanks

i am new to cookie decorating and have seen video tutorials of people outlining and flooding, and they flood with #2 or 3 tip i believe and leave some gaps then use the needle tool or tooth pick to fill them in. that way you can ensure you aren't flooding too much. otherwise if could run off the side.